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Homework Help: Algebra Problem

  1. Oct 21, 2007 #1
    Can't figure out how the example in the book is getting from one step to the next.

    Here's the problem
    2(8+216/x)(-216/x^2) + 2(x+27) = 0

    The next step
    (x+27)(1-1728/x^3) = 0

    First thing I did was divide out the two & got
    (8+216/x)(-216/x^2) + (x+27) = 0
    Then I multiplied out the left part
    -1728x^-2 + 46656x^-3 + (x+27) = 0
    This got me nowhere it seems.
    Then I tried to find a common denominator
    -1728x-46656/x + (x+27) = 0
    this is what I got when I multiplied it out & still nowhere it seems. Any help would be appreciated.
  2. jcsd
  3. Oct 22, 2007 #2


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    Staff Emeritus
    Science Advisor
    Gold Member

    Nope. This is wrong, so all that follows is also wrong.

    Next step:

    [tex] \frac {- 8 (216)} {x^2} - \frac {216^2} {x^3} + (x+27) =0 [/tex]

    now multiply through by [itex] x^3 [/itex] to get:
    [tex] -8(216)x - 216^2 + x^3 (x+27) = 0 [/tex]
    now you should be able to continue.
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